Dilip G Banhatti

Publications

• Getting more out of V/Vm than just the mean

  Dilip G Banhatti

  03/2011;

  Banhatti (2009) set down the procedure to derive cosmological number density n(z) from the differential distribution p(x) of the fractional luminosity volume relative to the maximum volume, x \equiv V/Vm (0 \leq x \leq 1), using a small sample of 76 quasars for illustrative purposes. This procedure ... [more] Banhatti (2009) set down the procedure to derive cosmological number density n(z) from the differential distribution p(x) of the fractional luminosity volume relative to the maximum volume, x \equiv V/Vm (0 \leq x \leq 1), using a small sample of 76 quasars for illustrative purposes. This procedure is here applied to a bigger sample of 286 quasars selected from Parkes half-Jansky flat-spectrum survey at 2.7 GHz (Drinkwater et al 1997). The values of n(z) are obtained for 8 values of redshift z from 0 to 3.5. The function n(z) can be interpreted in terms of redshift distribution obtained by integrating the radio luminosity function {\rho}(P, z) over luminosities P for the survey limiting flux density S0 = 0.5 Jy. Keywords. V/Vm - luminosity-volume - cosmological number density - redshift distribution - luminosity function - quasars

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• Application of slingshot model to the giant radio galaxy DA240 (Brief : DA 240 in slingshot model)

  S. Muthumeenal, Dilip G Banhatti

  05/2010;

  We attempt a slingshot model interpretation of the unusual association of some 1&1/3 dozen nonstellar galaxian objects around the parent optical galaxy of the giant radio galaxy DA 240 (= 0748.6+55.8 (J2000)). Similar interpretation may be possible for another large radio galaxy 3C 31 (= NGC 383... [more] We attempt a slingshot model interpretation of the unusual association of some 1&1/3 dozen nonstellar galaxian objects around the parent optical galaxy of the giant radio galaxy DA 240 (= 0748.6+55.8 (J2000)). Similar interpretation may be possible for another large radio galaxy 3C 31 (= NGC 383 = 0104.6+32.1 (1950.0)). Comment: 6 pages, 2 figures, based on S Muthumeenal's 2007 MPhil project; Keywords. active galaxy - radio galaxy - beam model - slingshot model

• Application of slingshot model to the giant radio galaxy DA240

  S. Muthumeenal, Dilip G Banhatti

  arXiv astro-ph/1005.4381. 01/2010;

  We attempt a slingshot model interpretation of the unusual association of some 1&1/3 dozen nonstellar galaxian objects around the parent optical galaxy of the giant radio galaxy DA 240 (= 0748.6+55.8 (J2000)). Similar interpretation may be possible for another large radio galaxy 3C 31 (= NGC 383... [more] We attempt a slingshot model interpretation of the unusual association of some 1&1/3 dozen nonstellar galaxian objects around the parent optical galaxy of the giant radio galaxy DA 240 (= 0748.6+55.8 (J2000)). Similar interpretation may be possible for another large radio galaxy 3C 31 (= NGC 383 = 0104.6+32.1 (1950.0)).

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• Effect of errors on arm asymmetry of doubles

  Dilip G Banhatti

  09/2009;

  Measured values of arm asymmetry parameter x = (theta> - theta<)/(theta> + theta<) of a double have appreciable random errors due to errors in positions of radio peaks & of the optically identified galaxy or quasar. These broaden the monotonic decreasing x-distribution g(x). In addit... [more] Measured values of arm asymmetry parameter x = (theta> - theta<)/(theta> + theta<) of a double have appreciable random errors due to errors in positions of radio peaks & of the optically identified galaxy or quasar. These broaden the monotonic decreasing x-distribution g(x). In addition, finite resolution & blending of complex structure leads to errors in recognizing peaks leading to systematic overestimate of x. Thus both random & systematic errors broaden g(x), & consequently broaden the distribution p(v) of derived hotspot separation speed v, & shift its peak to larger v, since p(v) = -v.g'(v). Keywords: active galaxies - double radio sources - bilateral symmetry - arm asymmetry Comment: 2 pages

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• Relation between positional & strength asymmetries of double radio sources associated with active galaxies

  Dilip G Banhatti

  09/2009;

  We bring out the identity between two ways of defining a single parameter to combine positional & strength asymmetries of extended extragalactic double radio sources associated with active galaxies. Thus, (r.s - 1)/[(1 + r).(1 + s)], combining arm ratio r (defined to be <= 1, i.e., shorter to... [more] We bring out the identity between two ways of defining a single parameter to combine positional & strength asymmetries of extended extragalactic double radio sources associated with active galaxies. Thus, (r.s - 1)/[(1 + r).(1 + s)], combining arm ratio r (defined to be <= 1, i.e., shorter to longer arm) & strength ratio s (in the sense closer to farther, so that it may be <, > or = 1), is identical to -(1/2)[(1 - fr)/(1 + fr) - t], where fr is strength ratio defined >= 1 (i.e., stronger to weaker), & t = +/- (Q - 1)/(Q + 1), +/- signs applying respectively to doubles with closer hotspot fainter & those with closer hotspot brighter, while Q is arm ratio defined >= 1. Keywords: active galaxies - double radio sources - bilateral symmetry - arm ratio - flux ratio Comment: 3 pages

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• Cosmological number density n(z) in depth z from p(V/Vm) distribution

  Dilip G. Banhatti

  04/2009;

  Using distribution p(V/Vm) of V/Vm rather than just mean <V/Vm> in V/Vm-test leads directly to cosmological number density n(z). Calculation of n(z) from p(V/Vm) is illustrated using best sample (of 76 quasars) available in 1981, when method was developed. This is only illustrative, sample bei... [more] Using distribution p(V/Vm) of V/Vm rather than just mean <V/Vm> in V/Vm-test leads directly to cosmological number density n(z). Calculation of n(z) from p(V/Vm) is illustrated using best sample (of 76 quasars) available in 1981, when method was developed. This is only illustrative, sample being too small for any meaningful results. Keywords: V/Vm . luminosity volume . cosmological number density . V/Vm distribution

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• Cosmological number density in depth from V/Vm distribution

  Dilip G. Banhatti

  04/2009;

  Using distribution p(V/Vm) of V/Vm rather than just mean <V/Vm> in V/Vm-test leads directly to cosmological number density n(z). Calculation of n(z) from p(V/Vm) is illustrated using best sample (of 76 quasars) available in 1981, when method was developed. This is only illustrative, sample bei... [more] Using distribution p(V/Vm) of V/Vm rather than just mean <V/Vm> in V/Vm-test leads directly to cosmological number density n(z). Calculation of n(z) from p(V/Vm) is illustrated using best sample (of 76 quasars) available in 1981, when method was developed. This is only illustrative, sample being too small for any meaningful results. Keywords: V/Vm . luminosity volume . cosmological number density . V/Vm distribution

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• Derivation of the cosmological number density in depth from V/Vm distribution

  Dilip G. Banhatti

  04/2009;

  The classical cosmological V/Vm-test is introduced. Use of the differential distribution p(V/Vm) of the V/Vm-variable rather than just the mean <V/Vm> leads directly to the cosmological number density without any need for assumptions about the cosmological evolution of the underlying (quasar) ... [more] The classical cosmological V/Vm-test is introduced. Use of the differential distribution p(V/Vm) of the V/Vm-variable rather than just the mean <V/Vm> leads directly to the cosmological number density without any need for assumptions about the cosmological evolution of the underlying (quasar) population. Calculation of this number density n(z) from p(V/Vm) is illustrated using the best sample that was available in 1981, when this method was developed. This sample of 76 quasars is clearly too small for any meaningful results. The method will be later applied to a much larger cosmological sample to infer the cosmological number density n(z) as a function of the depth z. Keywords: V/Vm . luminosity volume . cosmological number density . V/Vm distribution

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• A model-independent technique to determine one-dimensional radio source structure from interplanetary scintillation (IPS) observations

  V R Venugopal, P K Manoharan, D G Banhatti, S Edwin Jayaraj

  03/2009;

  We outline a method of deriving one-dimensional phaseless visibility along solar wind direction from interplanetary scintillation power spectrum, together with the known visibility of a calibration source. The method is illustrated briefly. Details may be found in Edwin Jayaraj (1990).... [more] We outline a method of deriving one-dimensional phaseless visibility along solar wind direction from interplanetary scintillation power spectrum, together with the known visibility of a calibration source. The method is illustrated briefly. Details may be found in Edwin Jayaraj (1990).

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• Occultation of the radio source 2019+098 (3C411) by comet 1983e (Sugano-Saigusa-Fujikawa)

  S. Ananthakrishnan, Dilip G. Banhatti

  03/2009;

  [This cometary occultation observation from June 1983 remained to be formally reported due to other preoccupations of the authors. It was presented in seminars to colleagues at Ooty, Bangalore and elsewhere. We now write it up as we have been asked about it by various colleagues at various times, an... [more] [This cometary occultation observation from June 1983 remained to be formally reported due to other preoccupations of the authors. It was presented in seminars to colleagues at Ooty, Bangalore and elsewhere. We now write it up as we have been asked about it by various colleagues at various times, and feel we owe it to them to put it firmly on record.] We planned and observed with Ooty Radio Telescope the occultation with Comet 1983e Sugano-Saigusa-Fujikawa of the extragalactic radio source 2019+098 = 3C411. The results are presented formally for the first time, along with a brief account of other cometary occultations and general background of planning, execution and interpretation of such observations which will be useful for other future observers. The occultation occurred at 07:52 IST on 12th June 1983. It amounted to 25% peak to peak fluctuation in the flux density of the radio source. The rough predicted occultation time was 07:24 IST. We interpret the results after refining the occultation time to allow for various effects.

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• The luminosity-volume method : Derivation of the cosmological number density in depth from V/Vm distribution [Number density in depth from luminosity-volume]

  Dilip G. Banhatti

  03/2009;

  The classical cosmological V/Vm-test is introduced and elaborated. Use of the differential distribution p(V/Vm) of the V/Vm-variable rather than just the mean <V/Vm> leads directly to the cosmological number density without any need for assumptions about the cosmological evolution of the under... [more] The classical cosmological V/Vm-test is introduced and elaborated. Use of the differential distribution p(V/Vm) of the V/Vm-variable rather than just the mean <V/Vm> leads directly to the cosmological number density without any need for assumptions about the cosmological evolution of the underlying (quasar) population. Calculation of this number density n(z) from p(V/Vm) is illustrated using the best sample that was available in 1981, when this method was developed. This sample of 76 quasars is clearly too small for any meaningful results. The method will be later applied to a much larger cosmological sample to infer the cosmological number density n(z) as a function of the depth z. Keywords: V/Vm . luminosity volume . cosmological number density . V/Vm distribution

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• Neutrinos of non-zero rest mass and the equivalence principle

  D. G. Banhatti

  02/2009;

  Assuming that neutrinos of non-zero rest mass dominate the mass density in the universe, and also the mass density on the scale of clusters of galaxies, one obtains the upper limit m < 20 eV/c^2 on their mass, independent of the values of H_0 and q_0, and the lower limit m > 5 eV/c^2 independe... [more] Assuming that neutrinos of non-zero rest mass dominate the mass density in the universe, and also the mass density on the scale of clusters of galaxies, one obtains the upper limit m < 20 eV/c^2 on their mass, independent of the values of H_0 and q_0, and the lower limit m > 5 eV/c^2 independent of q_0 and almost independent of H_0. If they are not to dominate the mass density on the scale of binary galaxies and small groups of galaxies, one must have m < 14 eV/c2 independent of q0 and almost independent of H0. Going one step further, we allow neutrinos to have different gravitational and inertial masses so that r = gravitational / inertial mass. Then using m for the inertial mass, we have m.r^1/4 > 5 eV/c^2, m.r^(1/4) < 14 eV/c^2 and m.r < 20 eV/c^2, which together imply r < 6.3. For a specific value, say, 12 eV/c^2, for m, we have 0.03 < r < 1.7. Keywords: Neutrinos, rest mass, equivalence principle.

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• Mass Distribution, Rotation Curves and Gravity Theories

  Rahul Datta, Dilip G. Banhatti

  09/2008;

  {Comparison of mass density profiles of galaxies of varying sizes based on some gravity theories from observed galaxy rotation curves and assessing the need for dark matter.} We present an analysis of the rotation curves of five galaxies of varying galactic radii: NGC6822 (4.8 kpc), Large Magellanic... [more] {Comparison of mass density profiles of galaxies of varying sizes based on some gravity theories from observed galaxy rotation curves and assessing the need for dark matter.} We present an analysis of the rotation curves of five galaxies of varying galactic radii: NGC6822 (4.8 kpc), Large Magellanic Cloud (9 kpc), The Milky Way (17 kpc), NGC3198 (30 kpc) and UGC9133 (102.5 kpc). The mass and mass density profiles of these galaxies have been computed using the scientific computing s/w package MATLAB taking the already available velocity profiles of the galaxies as the input, and without considering any Dark Matter contribution. We have plotted these profiles after computing them according to three different theories of gravity (and dynamics): Newtonian (black line), Modified Newtonian Dynamics (MoND) (green line) and Vacuum Modified Gravity (red line). We also consider how the profile due to the Newtonian theory would modify if we take into account a small negative value of the Cosmological Constant (5 x 10^-56 cm^-2 from theory) (blue line). Comparing these mass and mass density profiles, we try to form an idea regarding what could be a realistic theory of gravity and whether we need Dark Matter to explain the results. Keywords : disk galaxy rotation curves, galaxy mass, mass density profile, dark matter, Newtonian theory, MoND, Vacuum Modified Gravity, negative cosmological constant

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• Newtonian mechanics & gravity fully model disk galaxy rotation curves without dark matter

  Dilip G. Banhatti

  07/2008;

  EGRET gamma-ray archival data used with GALPROP software show two ringlike structures in Milky Way Plane which roughly tally with distribution of stars ([1] & references therein). To understand fully the implications of this and similar results on detailed structure and rotation curve of especia... [more] EGRET gamma-ray archival data used with GALPROP software show two ringlike structures in Milky Way Plane which roughly tally with distribution of stars ([1] & references therein). To understand fully the implications of this and similar results on detailed structure and rotation curve of especially Milky Way Disk as well as rotation curves of other galaxies as derived from spatially resolved spectroscopic data-cubes, a re-examination of the basis of the connection between mass density and rotation curve is warranted. Kenneth F. Nicholson's approach [2], which uses only Newtonian dynamics & gravity, is presented.

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• Need for context-aware computing in astrophysics

  Dilip G. Banhatti

  06/2008;

  The example of disk galaxy rotation curves is given for inferring dark matter from redundant computational procedure because proper care of astrophysical and computational context was not taken. At least three attempts that take the context into account have not found adequate voice because of haste... [more] The example of disk galaxy rotation curves is given for inferring dark matter from redundant computational procedure because proper care of astrophysical and computational context was not taken. At least three attempts that take the context into account have not found adequate voice because of haste in wrongly concluding existence of dark matter on the part of even experts. This firmly entrenched view, prevalent for about 3/4ths of a century, has now become difficult to correct. The right context must be borne in mind at every step to avoid such a situation. Perhaps other examples exist. Keywords: dark matter; disk galaxy; rotation curve; context-awareness. Topics: Algorithms; Applications.

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• Luminosity volume test for compact steep spectrum radio sources

  V. K. Kapahi, D. G. Banhatti

  09/2007;

  We apply the V/Vm test to a subsample of compact steep-spectrum sources from a complete sample of radio sources selected at 2.7 GHz. We find that the <V/Vm> has a value intermediate between those found for samples of extended steep-spectrum sources and those of compact flat-spectrum sources. I... [more] We apply the V/Vm test to a subsample of compact steep-spectrum sources from a complete sample of radio sources selected at 2.7 GHz. We find that the <V/Vm> has a value intermediate between those found for samples of extended steep-spectrum sources and those of compact flat-spectrum sources. If the sample is split into two further classes of sources having more steep and less steep spectra, the <V/Vm> values for these then tally roughly with those found for the extended steep-spectrum and compact flat-spectrum classes of sources. Implications of this result are discussed.

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• Disk galaxy rotation curves and dark matter distribution

  Dilip G. Banhatti

  04/2007;

  After explaining the motivation for this article, I briefly recapitulate the methods used to determine, somewhat coarsely, the rotation curves of our Milky Way Galaxy and other spiral galaxies, especially in their outer parts, and the results of applying these methods. Recent observations and models... [more] After explaining the motivation for this article, I briefly recapitulate the methods used to determine, somewhat coarsely, the rotation curves of our Milky Way Galaxy and other spiral galaxies, especially in their outer parts, and the results of applying these methods. Recent observations and models of the very inner central parts of galaxian rotation curves are only briefly described. I then present the essential Newtonian theory of (disk) galaxy rotation curves. The next two sections present two numerical simulation schemes and brief results. Application of modified Newtonian dynamics to the outer parts of disk galaxies is then described. Finally, attempts to apply Einsteinian general relativity to the dynamics are summarized. The article ends with a summary and prospects for further work in this area.

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• Mercury transits Sun on 7 May 2003

  Dilip G. Banhatti

  Preprint. 01/2003; Private circulation:2 pages.

  The tiny disk of planet Mercury will move across the large half-degree wide disk of Sun during 5&1/4 hours on 7th May 2003. This event will be visible from the sunlit side of Earth, for example in India (10:43 to 16:02), Germany (07:13 to 13:32) & England (06:13 to 12:32).... [more] The tiny disk of planet Mercury will move across the large half-degree wide disk of Sun during 5&1/4 hours on 7th May 2003. This event will be visible from the sunlit side of Earth, for example in India (10:43 to 16:02), Germany (07:13 to 13:32) & England (06:13 to 12:32).

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  Some home-truths about small samples and counting statistics

  C. J. Salter, Dilip G. Banhatti

  Bulletin of the Astronomical Society of India. 01/2000; 28:363-365.

  Assessing a fluctuation in the sky density of astronomical objects uses counting (i.e., Poisson) statistics for estimating errors. For a finite sample, there is a limit to the maximum possible fluctuation from the mean in units of the rms. This maximum is derived, and an example is used to illustrat... [more] Assessing a fluctuation in the sky density of astronomical objects uses counting (i.e., Poisson) statistics for estimating errors. For a finite sample, there is a limit to the maximum possible fluctuation from the mean in units of the rms. This maximum is derived, and an example is used to illustrate these concepts.

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  Linear sizes and arm asymmetry of intrinsically symmetric doubles

  Dilip G. Banhatti

  Bulletin of the Astronomical Society of India. 01/2000; 28:367-369.

  In an intrinsically symmetric model, the distribution p_x(x) of the fractional arm difference of a sample of straight double radio sources reflects the distribution among the doubles of their orientations phi away from the line of sight. In a constant speed expansion model, the two distributions can... [more] In an intrinsically symmetric model, the distribution p_x(x) of the fractional arm difference of a sample of straight double radio sources reflects the distribution among the doubles of their orientations phi away from the line of sight. In a constant speed expansion model, the two distributions can be simply related, and the resultant distribution p_el(el) of the projected linear sizes el can be derived, to be compared with the observed distribution for the same sample. Such a calculation is illustrated using a sample of extended doubles. The model is perhaps more applicable to compact doubles. However, these are not yet numerous enough to construct usable samples.

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